• 한국철도학회:학술대회논문집
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• 한국철도학회 2000년도 추계학술대회 논문집
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• pp.521-526
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• 2000

Experimental study is conducted to clarify pressure variation of the passenger cabin of conventional train. These pressure variation may give rise to the ear-discomfort. Generally ear-discomfort has been considered as a problem related to high speed train. Because there is also a good progress to speed-up for conventional line, this isn't only a phenomena related to high speed train any longer. In this study, tile pressure variation of interior, gangway and exterior of saemaeul passenger car is measured using the atmospheric pressure sensors in Honam line. From the results of experiment, the pressure variation per second almost close in upon the limitation in the case of Noryong tunnel. Therefore, to accomplish speed-up for conventional train, it may be necessary to study a serial ventilating and the airtightness of carbody.

• 대한기계학회논문집B
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• 제32권12호
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• pp.915-923
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• 2008

The performance experiments for a microchannel printed circuit heat exchanger (PCHE) of high-performance and high-efficiency on the two technologies of micro photo-etching and diffusion bonding were performed in this study. The microchannel PCHE were experimentally investigated for Reynolds number in ranges of 100 $\sim$ 700 under various flow conditions in the hot side and the cold side. The inlet temperatures of the hot side were conducted in range of $40^{\circ}C\;{\sim}\;50^{\circ}C$ while that of the cold-side were fixed at $20^{\circ}C$. In the flow pattern, the counter flow was provided 6.8% and 10 $\sim$ 15% higher average heat transfer rate and heat transfer performance than the parallel flow, respectively. The average heat transfer rate, heat transfer performance and pressure drop increases with increasing Reynolds number in all the experiment. The increasing of inlet temperature in the experiment range has not an effect on the heat transfer performance while the pressure drop decrease slightly with that of inlet temperature. The experimental correlations to the heat transfer coefficient and pressure drop factor as a function of the Reynolds number have been suggested for the microchannel PCHE.

• Nuclear Engineering and Technology
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• 제45권1호
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• pp.53-60
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• 2013

Bentonite is generally used as a buffer material in high-level radioactive waste disposal facilities and consists of 50% quartz by weight. Quartz strongly affects the behavior of bentonite over very long periods. For this reason, quartz dissolution experiment was performed under high-pressure and high-alkalinity conditions based on the conditions found in a high-level radioactive waste disposal facility located deep underground. In this study, two quartz dissolution experiments were conducted on 1) quartz beads under low-pressure and high-alkalinity conditions and 2) a single quartz crystal under high-pressure and high-alkalinity conditions. Following the experiments, a confocal laser scanning microscope (CLSM) was used to observe the surfaces of experimental samples. Numerical analyses using the finite element method (FEM) were also performed to quantify the deformation of contact area. Quartz dissolution was observed in both experiments. This deformation was due to a concentrated compressive stress field, as indicated by the quartz deformation of the contact area through the FEM analysis. According to the numerical results, a high compressive stress field acted upon the neighboring contact area, which showed a rapid dissolution rate compared to other areas of the sample.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.650-654
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• 1997

This paper presents the experimental results of air pressure analysis around a high speed and large package pirn. The experimental system is constructed to measure around air pressure of a rotating pirn in highspeed. The experiment is carred out for the varios speeds. The results that, air pressure around rotating pirn increases as the speed increase, air prissure on the midle of the prin is larger than that on the both ends, and the force direction is opposite to the rotation dirction. The present results a useful to design the high speed, large package pirn winder.

• 한국약용작물학회지
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• 제20권3호
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• pp.171-176
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• 2012

This study was conducted to investigate the effect of atmosphere-leaf vapor pressure deficit (VPD) in Allium microdictyon Prokh. and Allium ochotense Prokh. The vapor pressure deficit (VPD) was rapidly increased with increasing temperature and decreasing relative humidity. Taken as a whole, the stomatal transpiration reaction was slightly late with increading of VPD. Maximum photosynthetic rate at high-VPD condition was 5.98 ${\mu}mol$ $CO_2{\cdot}m^{-2}{\cdot}s^{-1}$ in Allium microdictyon, which was a little lower than 6.59 ${\mu}mol$ $CO_2{\cdot}m^{-2}{\cdot}s^{-1}$ in Allium ochotense, respectively. After 2 p.m, stomatal transpiration of Allium microdictyon at the high VPD condition were rapidly decreased. Ci/Ca began to decline sharply at 8 a.m and showed the lowest value at 2 p.m, The results showed that Ci/Ca decreased with being used $CO_2$ in the mesophyll intercellular space for photosynthesis. In high VPD condition, The water potential values showed the highest at 5 a.m, and the lowest at 1 p.m in high VPD condition. The water saturation deficits (WSD) in high VPD condition showed about 1.5 times higher than in low VPD condition. The results indicated that physiological activities in Allium microdictyon is more limited from high VPD conditions.

• 대한기계학회논문집B
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• 제23권6호
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• pp.722-733
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• 1999

The wall pressure fluctuations of a turbulent boundary layer over a flat plate have been investigated in an anechoic wind tunnel facility. The anechoic wind tunnel consists of acoustically-lined duct, muffler, and splitter-type silencer for noise suppression and vanes for reducing head losses involved. To improve spectra characteristics in high frequency range, a 1/8" pressure-type microphone sensor, which has a pin-holed cap of various diameters, was employed in this experiment. It was shown that the pin-holed microphone sensor with a dimensionless diameter $d^+$ of 7.1 resolved the high frequency pressure fluctuations most effectively among ones with various pin-hole diameters. The measured wall pressure spectra in terms of three types of scaling parameters were in good agreement with other experimental and numerical results. The pressure events of high amplitude were found to contribute to total fluctuating pressure energies in the turbulent boundary layer significantly and supposed to radiate to the far-field effectively.

• 한국기계가공학회지
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• 제16권6호
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• pp.81-86
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• 2017

The high-pressure resin transfer molding (HP-RTM) process has a very effective for the mass production of carbon fiber reinforced plastic (CFRP) for light weight in the automotive industry. In developing robust equipment, new process and fast cure matrix systems reduces significantly the cycle time less than 5 minutes in recent years. This paper describes the cavity pressure, temperature and molding characteristics of the HP-RTM process. The HP-RTM mold was equipped with two cavity pressure sensors and three temperature sensors. The cavity pressure characteristics of the HP-RTM injection, pressurization, and curing processes were studied. This experiment was conducted with selected process parameters such as mold cap size, maximum press force, and injection volume. Consequently, this monitoring method provides correlations between the selected process parameters and final forming characteristics in this work.

• 소성∙가공
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• 제26권5호
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• pp.314-322
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• 2017

In the high-speed forming analysis, dynamic material properties considering a high strain rate are required. The split Hopkinson pressure bar (SHPB) experiment was performed for measuring dynamic material properties under high strain rate. The pulse shaping method was used to improve the accuracy of the SHPB experiment. A pulse shaper attached to the front of the incident bar was used for specimen dynamic stress equilibrium through stress wave control. Numerical analysis and SHPB test were performed to verify whether the pulse shaper affects the dynamic stress equilibrium in copper and Al6061 specimens. The results of SHPB test and numerical analysis show that the pulse shaper contributes to the dynamic stress equilibrium. Based on the improved stress equilibrium using a pulse shaper, the flow stress curves for copper and Al6061 materials were obtained at strain rates of 1344.4/sec and 1291.6/sec, respectively.

• Journal of Nutrition and Health
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• 제32권1호
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• pp.30-39
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• 1999

This study was designed to investigate the effect of Ca supplementation of 1,000mg per day for 53 weeks on lipid, Na, and K metabolism and on blood pressure in postmenopausal women. The subjects were 12 healthy women aged from 60 to 70 years. They were divided into two groups : the placebo(control group) and the Ca supplemented(1,000 mg/day) group(Ca group). Metabolic studies were conducted twice in the 1st and the 53rd weeks. The results were as follows : Serum triglyceride, total cholesterol and LDL-choesterol levels tended to be decreased after the experiment. Serum VLDL-cholesterol lowering effect was observed with Ca supplementation(p<0.05), and also the significantly elevated HDL/(LDL+VLDL) ratio in Ca supplemented subjects whose average Na intake was as high as 4.9g per day. This phenomena was accompanied with increased Na retention and increased Na excretion in feces, but with decreased urinary Na in Ca supplemented group. However, considering much higher Na reteniton in the control group at the end of experiment(control va Ca ; 1272.3mg vs 732.9mg), Ca supplementation may have some beneficial effects on Na blance. Serum aldosterone level increased significantly in the Ca group after the exsperiment(p<0.05). With these normotensive subjects, there were no level increased significantly in the Ca group after the experiment(p<0.05). With these normotensive subjects, there were no pronounced effect of Ca supplementation on blood pressure, however, decrease in diastolic blood pressure were observed at the 14th week and end of the experiment(p<0.05). In summary, the Ca supplementation on postmenopausal Koran women appears to exert a desirables effect on blood lipid patterns related to the coronary heart diseases and to be beneficial in controlling diastolic blood pressure. Further studies with hypertensive or/and hyperlipidemic subjects are required to clarify the effect of Ca supplementation in Koreans.

• 전기의세계
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• 제30권6호
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• pp.357-365
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• 1981

When electronegative gas SF$_{6}$ is dissolved and charged with insulating oil, the effect caused in the process by electronegative characteristic is studied and also the pressure effect caused by electronegative SF$_{6}$ acting on the liquid-level is examined respectively. When inert gas Ar is used to find a pressure effect acting on the liquid-level, its effect on dielectric strength is considered in the experiment. With three kinds of impulse voltage different in the duration of wave front and wave tail, a brief experiment if carried out ot see the effects on the dielectric breakdown characteristic as the wave is changing; either if I$_{2}$ and SF$_{6}$ are added to the insulating oil, or if the oil pressure is increased by Ar the dielectric strength becomes great and the longer the duration of wave front is, the greater the increase of the breakdown voltage, because I$_{2}$ added by a small quantity brings about some hirderance in the formation of gas phase. Likewise, the greater the changed pressure is, the greater the incerase of the breakdown voltage. When SF$_{6}$ is charged, the electronegative characteristic is prevailing at the time of low balanced pressure, and the pressure effect at the time of high balanced pressure.ressure.